The Cantar de mio Cid (El Cid) recounts the heroic deeds of the Cid, an exiled member of the lower nobility who wins back his king's favor by battling the Islamic inhabitants of Spain. Based on the exploits of a historical personage, Rodrigo (Ruy) Diaz de Vivar, who lived from 1040-1099, this epic offers an important example of the interaction of history and literature in the Middle Ages.

The Cid is best known for its interweaving of irony, heroic drama, and a rare strain of realism that incorporates multifaceted portraits of Moors, Jews, and Christians. One of the oldest Spanish documents in existence, it is also the only Spanish epic to have survived almost intact. It is contained in a fourteenth-century manuscript, which bears the date 1207, most likely referring to an earlier version of the poem that was copied in the later book. Several accounts of the Cid's life, however, exist before this epic poem was written in manuscript form. Two Latin poems, one written before the Cid's death, and the other just after, chronicle his life. He is mentioned in Arabic sources, and his fame endured throughout the Middle Ages, in works of varying quality.

The Cantar de mio Cid has been well-received as a work of literature for several centuries. The French dramatist Pierre Corneille's famous version of the poem (Le Cid, 1637) demonstrates its lasting popularity in Europe. Printed editions of the poem have existed since the eighteenth century; a ground breaking newer edition (1908) was published by the prominent Spanish medievalist Ram6n Menendez Pidal. Menendez Pidal's influential work on the Cid ensured an international critical audience for this epic. A poem which treats basic themes such as national and religious identity, family honor, and personal prowess, the Cidhas earned a lasting place in the ranks of great world literature.